1------------------------------------------------------------------------------ 2 T H E /proc F I L E S Y S T E M 3------------------------------------------------------------------------------ 4/proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 5 Bodo Bauer <bb@ricochet.net> 6 72.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 8move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 9------------------------------------------------------------------------------ 10Version 1.3 Kernel version 2.2.12 11 Kernel version 2.4.0-test11-pre4 12------------------------------------------------------------------------------ 13fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009 14 15Table of Contents 16----------------- 17 18 0 Preface 19 0.1 Introduction/Credits 20 0.2 Legal Stuff 21 22 1 Collecting System Information 23 1.1 Process-Specific Subdirectories 24 1.2 Kernel data 25 1.3 IDE devices in /proc/ide 26 1.4 Networking info in /proc/net 27 1.5 SCSI info 28 1.6 Parallel port info in /proc/parport 29 1.7 TTY info in /proc/tty 30 1.8 Miscellaneous kernel statistics in /proc/stat 31 1.9 Ext4 file system parameters 32 33 2 Modifying System Parameters 34 35 3 Per-Process Parameters 36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer 37 score 38 3.2 /proc/<pid>/oom_score - Display current oom-killer score 39 3.3 /proc/<pid>/io - Display the IO accounting fields 40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 41 3.5 /proc/<pid>/mountinfo - Information about mounts 42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 43 44 45------------------------------------------------------------------------------ 46Preface 47------------------------------------------------------------------------------ 48 490.1 Introduction/Credits 50------------------------ 51 52This documentation is part of a soon (or so we hope) to be released book on 53the SuSE Linux distribution. As there is no complete documentation for the 54/proc file system and we've used many freely available sources to write these 55chapters, it seems only fair to give the work back to the Linux community. 56This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 57afraid it's still far from complete, but we hope it will be useful. As far as 58we know, it is the first 'all-in-one' document about the /proc file system. It 59is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 60SPARC, AXP, etc., features, you probably won't find what you are looking for. 61It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 62additions and patches are welcome and will be added to this document if you 63mail them to Bodo. 64 65We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 66other people for help compiling this documentation. We'd also like to extend a 67special thank you to Andi Kleen for documentation, which we relied on heavily 68to create this document, as well as the additional information he provided. 69Thanks to everybody else who contributed source or docs to the Linux kernel 70and helped create a great piece of software... :) 71 72If you have any comments, corrections or additions, please don't hesitate to 73contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this 74document. 75 76The latest version of this document is available online at 77http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 78 79If the above direction does not works for you, you could try the kernel 80mailing list at linux-kernel@vger.kernel.org and/or try to reach me at 81comandante@zaralinux.com. 82 830.2 Legal Stuff 84--------------- 85 86We don't guarantee the correctness of this document, and if you come to us 87complaining about how you screwed up your system because of incorrect 88documentation, we won't feel responsible... 89 90------------------------------------------------------------------------------ 91CHAPTER 1: COLLECTING SYSTEM INFORMATION 92------------------------------------------------------------------------------ 93 94------------------------------------------------------------------------------ 95In This Chapter 96------------------------------------------------------------------------------ 97* Investigating the properties of the pseudo file system /proc and its 98 ability to provide information on the running Linux system 99* Examining /proc's structure 100* Uncovering various information about the kernel and the processes running 101 on the system 102------------------------------------------------------------------------------ 103 104 105The proc file system acts as an interface to internal data structures in the 106kernel. It can be used to obtain information about the system and to change 107certain kernel parameters at runtime (sysctl). 108 109First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 110show you how you can use /proc/sys to change settings. 111 1121.1 Process-Specific Subdirectories 113----------------------------------- 114 115The directory /proc contains (among other things) one subdirectory for each 116process running on the system, which is named after the process ID (PID). 117 118The link self points to the process reading the file system. Each process 119subdirectory has the entries listed in Table 1-1. 120 121 122Table 1-1: Process specific entries in /proc 123.............................................................................. 124 File Content 125 clear_refs Clears page referenced bits shown in smaps output 126 cmdline Command line arguments 127 cpu Current and last cpu in which it was executed (2.4)(smp) 128 cwd Link to the current working directory 129 environ Values of environment variables 130 exe Link to the executable of this process 131 fd Directory, which contains all file descriptors 132 maps Memory maps to executables and library files (2.4) 133 mem Memory held by this process 134 root Link to the root directory of this process 135 stat Process status 136 statm Process memory status information 137 status Process status in human readable form 138 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan 139 pagemap Page table 140 stack Report full stack trace, enable via CONFIG_STACKTRACE 141 smaps a extension based on maps, showing the memory consumption of 142 each mapping 143.............................................................................. 144 145For example, to get the status information of a process, all you have to do is 146read the file /proc/PID/status: 147 148 >cat /proc/self/status 149 Name: cat 150 State: R (running) 151 Tgid: 5452 152 Pid: 5452 153 PPid: 743 154 TracerPid: 0 (2.4) 155 Uid: 501 501 501 501 156 Gid: 100 100 100 100 157 FDSize: 256 158 Groups: 100 14 16 159 VmPeak: 5004 kB 160 VmSize: 5004 kB 161 VmLck: 0 kB 162 VmHWM: 476 kB 163 VmRSS: 476 kB 164 VmData: 156 kB 165 VmStk: 88 kB 166 VmExe: 68 kB 167 VmLib: 1412 kB 168 VmPTE: 20 kb 169 VmSwap: 0 kB 170 Threads: 1 171 SigQ: 0/28578 172 SigPnd: 0000000000000000 173 ShdPnd: 0000000000000000 174 SigBlk: 0000000000000000 175 SigIgn: 0000000000000000 176 SigCgt: 0000000000000000 177 CapInh: 00000000fffffeff 178 CapPrm: 0000000000000000 179 CapEff: 0000000000000000 180 CapBnd: ffffffffffffffff 181 voluntary_ctxt_switches: 0 182 nonvoluntary_ctxt_switches: 1 183 184This shows you nearly the same information you would get if you viewed it with 185the ps command. In fact, ps uses the proc file system to obtain its 186information. But you get a more detailed view of the process by reading the 187file /proc/PID/status. It fields are described in table 1-2. 188 189The statm file contains more detailed information about the process 190memory usage. Its seven fields are explained in Table 1-3. The stat file 191contains details information about the process itself. Its fields are 192explained in Table 1-4. 193 194(for SMP CONFIG users) 195For making accounting scalable, RSS related information are handled in 196asynchronous manner and the vaule may not be very precise. To see a precise 197snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 198It's slow but very precise. 199 200Table 1-2: Contents of the status files (as of 2.6.30-rc7) 201.............................................................................. 202 Field Content 203 Name filename of the executable 204 State state (R is running, S is sleeping, D is sleeping 205 in an uninterruptible wait, Z is zombie, 206 T is traced or stopped) 207 Tgid thread group ID 208 Pid process id 209 PPid process id of the parent process 210 TracerPid PID of process tracing this process (0 if not) 211 Uid Real, effective, saved set, and file system UIDs 212 Gid Real, effective, saved set, and file system GIDs 213 FDSize number of file descriptor slots currently allocated 214 Groups supplementary group list 215 VmPeak peak virtual memory size 216 VmSize total program size 217 VmLck locked memory size 218 VmHWM peak resident set size ("high water mark") 219 VmRSS size of memory portions 220 VmData size of data, stack, and text segments 221 VmStk size of data, stack, and text segments 222 VmExe size of text segment 223 VmLib size of shared library code 224 VmPTE size of page table entries 225 VmSwap size of swap usage (the number of referred swapents) 226 Threads number of threads 227 SigQ number of signals queued/max. number for queue 228 SigPnd bitmap of pending signals for the thread 229 ShdPnd bitmap of shared pending signals for the process 230 SigBlk bitmap of blocked signals 231 SigIgn bitmap of ignored signals 232 SigCgt bitmap of catched signals 233 CapInh bitmap of inheritable capabilities 234 CapPrm bitmap of permitted capabilities 235 CapEff bitmap of effective capabilities 236 CapBnd bitmap of capabilities bounding set 237 Cpus_allowed mask of CPUs on which this process may run 238 Cpus_allowed_list Same as previous, but in "list format" 239 Mems_allowed mask of memory nodes allowed to this process 240 Mems_allowed_list Same as previous, but in "list format" 241 voluntary_ctxt_switches number of voluntary context switches 242 nonvoluntary_ctxt_switches number of non voluntary context switches 243.............................................................................. 244 245Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 246.............................................................................. 247 Field Content 248 size total program size (pages) (same as VmSize in status) 249 resident size of memory portions (pages) (same as VmRSS in status) 250 shared number of pages that are shared (i.e. backed by a file) 251 trs number of pages that are 'code' (not including libs; broken, 252 includes data segment) 253 lrs number of pages of library (always 0 on 2.6) 254 drs number of pages of data/stack (including libs; broken, 255 includes library text) 256 dt number of dirty pages (always 0 on 2.6) 257.............................................................................. 258 259 260Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 261.............................................................................. 262 Field Content 263 pid process id 264 tcomm filename of the executable 265 state state (R is running, S is sleeping, D is sleeping in an 266 uninterruptible wait, Z is zombie, T is traced or stopped) 267 ppid process id of the parent process 268 pgrp pgrp of the process 269 sid session id 270 tty_nr tty the process uses 271 tty_pgrp pgrp of the tty 272 flags task flags 273 min_flt number of minor faults 274 cmin_flt number of minor faults with child's 275 maj_flt number of major faults 276 cmaj_flt number of major faults with child's 277 utime user mode jiffies 278 stime kernel mode jiffies 279 cutime user mode jiffies with child's 280 cstime kernel mode jiffies with child's 281 priority priority level 282 nice nice level 283 num_threads number of threads 284 it_real_value (obsolete, always 0) 285 start_time time the process started after system boot 286 vsize virtual memory size 287 rss resident set memory size 288 rsslim current limit in bytes on the rss 289 start_code address above which program text can run 290 end_code address below which program text can run 291 start_stack address of the start of the stack 292 esp current value of ESP 293 eip current value of EIP 294 pending bitmap of pending signals 295 blocked bitmap of blocked signals 296 sigign bitmap of ignored signals 297 sigcatch bitmap of catched signals 298 wchan address where process went to sleep 299 0 (place holder) 300 0 (place holder) 301 exit_signal signal to send to parent thread on exit 302 task_cpu which CPU the task is scheduled on 303 rt_priority realtime priority 304 policy scheduling policy (man sched_setscheduler) 305 blkio_ticks time spent waiting for block IO 306 gtime guest time of the task in jiffies 307 cgtime guest time of the task children in jiffies 308.............................................................................. 309 310The /proc/PID/maps file containing the currently mapped memory regions and 311their access permissions. 312 313The format is: 314 315address perms offset dev inode pathname 316 31708048000-08049000 r-xp 00000000 03:00 8312 /opt/test 31808049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 3190804a000-0806b000 rw-p 00000000 00:00 0 [heap] 320a7cb1000-a7cb2000 ---p 00000000 00:00 0 321a7cb2000-a7eb2000 rw-p 00000000 00:00 0 322a7eb2000-a7eb3000 ---p 00000000 00:00 0 323a7eb3000-a7ed5000 rw-p 00000000 00:00 0 324a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 325a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 326a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 327a800b000-a800e000 rw-p 00000000 00:00 0 328a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 329a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 330a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 331a8024000-a8027000 rw-p 00000000 00:00 0 332a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 333a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 334a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 335aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 336ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 337 338where "address" is the address space in the process that it occupies, "perms" 339is a set of permissions: 340 341 r = read 342 w = write 343 x = execute 344 s = shared 345 p = private (copy on write) 346 347"offset" is the offset into the mapping, "dev" is the device (major:minor), and 348"inode" is the inode on that device. 0 indicates that no inode is associated 349with the memory region, as the case would be with BSS (uninitialized data). 350The "pathname" shows the name associated file for this mapping. If the mapping 351is not associated with a file: 352 353 [heap] = the heap of the program 354 [stack] = the stack of the main process 355 [vdso] = the "virtual dynamic shared object", 356 the kernel system call handler 357 358 or if empty, the mapping is anonymous. 359 360 361The /proc/PID/smaps is an extension based on maps, showing the memory 362consumption for each of the process's mappings. For each of mappings there 363is a series of lines such as the following: 364 36508048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 366Size: 1084 kB 367Rss: 892 kB 368Pss: 374 kB 369Shared_Clean: 892 kB 370Shared_Dirty: 0 kB 371Private_Clean: 0 kB 372Private_Dirty: 0 kB 373Referenced: 892 kB 374Anonymous: 0 kB 375Swap: 0 kB 376KernelPageSize: 4 kB 377MMUPageSize: 4 kB 378Locked: 374 kB 379 380The first of these lines shows the same information as is displayed for the 381mapping in /proc/PID/maps. The remaining lines show the size of the mapping 382(size), the amount of the mapping that is currently resident in RAM (RSS), the 383process' proportional share of this mapping (PSS), the number of clean and 384dirty private pages in the mapping. Note that even a page which is part of a 385MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used 386by only one process, is accounted as private and not as shared. "Referenced" 387indicates the amount of memory currently marked as referenced or accessed. 388"Anonymous" shows the amount of memory that does not belong to any file. Even 389a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE 390and a page is modified, the file page is replaced by a private anonymous copy. 391"Swap" shows how much would-be-anonymous memory is also used, but out on 392swap. 393 394This file is only present if the CONFIG_MMU kernel configuration option is 395enabled. 396 397The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 398bits on both physical and virtual pages associated with a process. 399To clear the bits for all the pages associated with the process 400 > echo 1 > /proc/PID/clear_refs 401 402To clear the bits for the anonymous pages associated with the process 403 > echo 2 > /proc/PID/clear_refs 404 405To clear the bits for the file mapped pages associated with the process 406 > echo 3 > /proc/PID/clear_refs 407Any other value written to /proc/PID/clear_refs will have no effect. 408 409The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags 410using /proc/kpageflags and number of times a page is mapped using 411/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt. 412 4131.2 Kernel data 414--------------- 415 416Similar to the process entries, the kernel data files give information about 417the running kernel. The files used to obtain this information are contained in 418/proc and are listed in Table 1-5. Not all of these will be present in your 419system. It depends on the kernel configuration and the loaded modules, which 420files are there, and which are missing. 421 422Table 1-5: Kernel info in /proc 423.............................................................................. 424 File Content 425 apm Advanced power management info 426 buddyinfo Kernel memory allocator information (see text) (2.5) 427 bus Directory containing bus specific information 428 cmdline Kernel command line 429 cpuinfo Info about the CPU 430 devices Available devices (block and character) 431 dma Used DMS channels 432 filesystems Supported filesystems 433 driver Various drivers grouped here, currently rtc (2.4) 434 execdomains Execdomains, related to security (2.4) 435 fb Frame Buffer devices (2.4) 436 fs File system parameters, currently nfs/exports (2.4) 437 ide Directory containing info about the IDE subsystem 438 interrupts Interrupt usage 439 iomem Memory map (2.4) 440 ioports I/O port usage 441 irq Masks for irq to cpu affinity (2.4)(smp?) 442 isapnp ISA PnP (Plug&Play) Info (2.4) 443 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 444 kmsg Kernel messages 445 ksyms Kernel symbol table 446 loadavg Load average of last 1, 5 & 15 minutes 447 locks Kernel locks 448 meminfo Memory info 449 misc Miscellaneous 450 modules List of loaded modules 451 mounts Mounted filesystems 452 net Networking info (see text) 453 pagetypeinfo Additional page allocator information (see text) (2.5) 454 partitions Table of partitions known to the system 455 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 456 decoupled by lspci (2.4) 457 rtc Real time clock 458 scsi SCSI info (see text) 459 slabinfo Slab pool info 460 softirqs softirq usage 461 stat Overall statistics 462 swaps Swap space utilization 463 sys See chapter 2 464 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 465 tty Info of tty drivers 466 uptime System uptime 467 version Kernel version 468 video bttv info of video resources (2.4) 469 vmallocinfo Show vmalloced areas 470.............................................................................. 471 472You can, for example, check which interrupts are currently in use and what 473they are used for by looking in the file /proc/interrupts: 474 475 > cat /proc/interrupts 476 CPU0 477 0: 8728810 XT-PIC timer 478 1: 895 XT-PIC keyboard 479 2: 0 XT-PIC cascade 480 3: 531695 XT-PIC aha152x 481 4: 2014133 XT-PIC serial 482 5: 44401 XT-PIC pcnet_cs 483 8: 2 XT-PIC rtc 484 11: 8 XT-PIC i82365 485 12: 182918 XT-PIC PS/2 Mouse 486 13: 1 XT-PIC fpu 487 14: 1232265 XT-PIC ide0 488 15: 7 XT-PIC ide1 489 NMI: 0 490 491In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 492output of a SMP machine): 493 494 > cat /proc/interrupts 495 496 CPU0 CPU1 497 0: 1243498 1214548 IO-APIC-edge timer 498 1: 8949 8958 IO-APIC-edge keyboard 499 2: 0 0 XT-PIC cascade 500 5: 11286 10161 IO-APIC-edge soundblaster 501 8: 1 0 IO-APIC-edge rtc 502 9: 27422 27407 IO-APIC-edge 3c503 503 12: 113645 113873 IO-APIC-edge PS/2 Mouse 504 13: 0 0 XT-PIC fpu 505 14: 22491 24012 IO-APIC-edge ide0 506 15: 2183 2415 IO-APIC-edge ide1 507 17: 30564 30414 IO-APIC-level eth0 508 18: 177 164 IO-APIC-level bttv 509 NMI: 2457961 2457959 510 LOC: 2457882 2457881 511 ERR: 2155 512 513NMI is incremented in this case because every timer interrupt generates a NMI 514(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 515 516LOC is the local interrupt counter of the internal APIC of every CPU. 517 518ERR is incremented in the case of errors in the IO-APIC bus (the bus that 519connects the CPUs in a SMP system. This means that an error has been detected, 520the IO-APIC automatically retry the transmission, so it should not be a big 521problem, but you should read the SMP-FAQ. 522 523In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 524/proc/interrupts to display every IRQ vector in use by the system, not 525just those considered 'most important'. The new vectors are: 526 527 THR -- interrupt raised when a machine check threshold counter 528 (typically counting ECC corrected errors of memory or cache) exceeds 529 a configurable threshold. Only available on some systems. 530 531 TRM -- a thermal event interrupt occurs when a temperature threshold 532 has been exceeded for the CPU. This interrupt may also be generated 533 when the temperature drops back to normal. 534 535 SPU -- a spurious interrupt is some interrupt that was raised then lowered 536 by some IO device before it could be fully processed by the APIC. Hence 537 the APIC sees the interrupt but does not know what device it came from. 538 For this case the APIC will generate the interrupt with a IRQ vector 539 of 0xff. This might also be generated by chipset bugs. 540 541 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are 542 sent from one CPU to another per the needs of the OS. Typically, 543 their statistics are used by kernel developers and interested users to 544 determine the occurrence of interrupts of the given type. 545 546The above IRQ vectors are displayed only when relevant. For example, 547the threshold vector does not exist on x86_64 platforms. Others are 548suppressed when the system is a uniprocessor. As of this writing, only 549i386 and x86_64 platforms support the new IRQ vector displays. 550 551Of some interest is the introduction of the /proc/irq directory to 2.4. 552It could be used to set IRQ to CPU affinity, this means that you can "hook" an 553IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 554irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 555prof_cpu_mask. 556 557For example 558 > ls /proc/irq/ 559 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 560 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 561 > ls /proc/irq/0/ 562 smp_affinity 563 564smp_affinity is a bitmask, in which you can specify which CPUs can handle the 565IRQ, you can set it by doing: 566 567 > echo 1 > /proc/irq/10/smp_affinity 568 569This means that only the first CPU will handle the IRQ, but you can also echo 5705 which means that only the first and fourth CPU can handle the IRQ. 571 572The contents of each smp_affinity file is the same by default: 573 574 > cat /proc/irq/0/smp_affinity 575 ffffffff 576 577There is an alternate interface, smp_affinity_list which allows specifying 578a cpu range instead of a bitmask: 579 580 > cat /proc/irq/0/smp_affinity_list 581 1024-1031 582 583The default_smp_affinity mask applies to all non-active IRQs, which are the 584IRQs which have not yet been allocated/activated, and hence which lack a 585/proc/irq/[0-9]* directory. 586 587The node file on an SMP system shows the node to which the device using the IRQ 588reports itself as being attached. This hardware locality information does not 589include information about any possible driver locality preference. 590 591prof_cpu_mask specifies which CPUs are to be profiled by the system wide 592profiler. Default value is ffffffff (all cpus if there are only 32 of them). 593 594The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 595between all the CPUs which are allowed to handle it. As usual the kernel has 596more info than you and does a better job than you, so the defaults are the 597best choice for almost everyone. [Note this applies only to those IO-APIC's 598that support "Round Robin" interrupt distribution.] 599 600There are three more important subdirectories in /proc: net, scsi, and sys. 601The general rule is that the contents, or even the existence of these 602directories, depend on your kernel configuration. If SCSI is not enabled, the 603directory scsi may not exist. The same is true with the net, which is there 604only when networking support is present in the running kernel. 605 606The slabinfo file gives information about memory usage at the slab level. 607Linux uses slab pools for memory management above page level in version 2.2. 608Commonly used objects have their own slab pool (such as network buffers, 609directory cache, and so on). 610 611.............................................................................. 612 613> cat /proc/buddyinfo 614 615Node 0, zone DMA 0 4 5 4 4 3 ... 616Node 0, zone Normal 1 0 0 1 101 8 ... 617Node 0, zone HighMem 2 0 0 1 1 0 ... 618 619External fragmentation is a problem under some workloads, and buddyinfo is a 620useful tool for helping diagnose these problems. Buddyinfo will give you a 621clue as to how big an area you can safely allocate, or why a previous 622allocation failed. 623 624Each column represents the number of pages of a certain order which are 625available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 626ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 627available in ZONE_NORMAL, etc... 628 629More information relevant to external fragmentation can be found in 630pagetypeinfo. 631 632> cat /proc/pagetypeinfo 633Page block order: 9 634Pages per block: 512 635 636Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 637Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 638Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 639Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 640Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 641Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 642Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 643Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 644Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 645Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 646Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 647 648Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 649Node 0, zone DMA 2 0 5 1 0 650Node 0, zone DMA32 41 6 967 2 0 651 652Fragmentation avoidance in the kernel works by grouping pages of different 653migrate types into the same contiguous regions of memory called page blocks. 654A page block is typically the size of the default hugepage size e.g. 2MB on 655X86-64. By keeping pages grouped based on their ability to move, the kernel 656can reclaim pages within a page block to satisfy a high-order allocation. 657 658The pagetypinfo begins with information on the size of a page block. It 659then gives the same type of information as buddyinfo except broken down 660by migrate-type and finishes with details on how many page blocks of each 661type exist. 662 663If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 664from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can 665make an estimate of the likely number of huge pages that can be allocated 666at a given point in time. All the "Movable" blocks should be allocatable 667unless memory has been mlock()'d. Some of the Reclaimable blocks should 668also be allocatable although a lot of filesystem metadata may have to be 669reclaimed to achieve this. 670 671.............................................................................. 672 673meminfo: 674 675Provides information about distribution and utilization of memory. This 676varies by architecture and compile options. The following is from a 67716GB PIII, which has highmem enabled. You may not have all of these fields. 678 679> cat /proc/meminfo 680 681The "Locked" indicates whether the mapping is locked in memory or not. 682 683 684MemTotal: 16344972 kB 685MemFree: 13634064 kB 686Buffers: 3656 kB 687Cached: 1195708 kB 688SwapCached: 0 kB 689Active: 891636 kB 690Inactive: 1077224 kB 691HighTotal: 15597528 kB 692HighFree: 13629632 kB 693LowTotal: 747444 kB 694LowFree: 4432 kB 695SwapTotal: 0 kB 696SwapFree: 0 kB 697Dirty: 968 kB 698Writeback: 0 kB 699AnonPages: 861800 kB 700Mapped: 280372 kB 701Slab: 284364 kB 702SReclaimable: 159856 kB 703SUnreclaim: 124508 kB 704PageTables: 24448 kB 705NFS_Unstable: 0 kB 706Bounce: 0 kB 707WritebackTmp: 0 kB 708CommitLimit: 7669796 kB 709Committed_AS: 100056 kB 710VmallocTotal: 112216 kB 711VmallocUsed: 428 kB 712VmallocChunk: 111088 kB 713 714 MemTotal: Total usable ram (i.e. physical ram minus a few reserved 715 bits and the kernel binary code) 716 MemFree: The sum of LowFree+HighFree 717 Buffers: Relatively temporary storage for raw disk blocks 718 shouldn't get tremendously large (20MB or so) 719 Cached: in-memory cache for files read from the disk (the 720 pagecache). Doesn't include SwapCached 721 SwapCached: Memory that once was swapped out, is swapped back in but 722 still also is in the swapfile (if memory is needed it 723 doesn't need to be swapped out AGAIN because it is already 724 in the swapfile. This saves I/O) 725 Active: Memory that has been used more recently and usually not 726 reclaimed unless absolutely necessary. 727 Inactive: Memory which has been less recently used. It is more 728 eligible to be reclaimed for other purposes 729 HighTotal: 730 HighFree: Highmem is all memory above ~860MB of physical memory 731 Highmem areas are for use by userspace programs, or 732 for the pagecache. The kernel must use tricks to access 733 this memory, making it slower to access than lowmem. 734 LowTotal: 735 LowFree: Lowmem is memory which can be used for everything that 736 highmem can be used for, but it is also available for the 737 kernel's use for its own data structures. Among many 738 other things, it is where everything from the Slab is 739 allocated. Bad things happen when you're out of lowmem. 740 SwapTotal: total amount of swap space available 741 SwapFree: Memory which has been evicted from RAM, and is temporarily 742 on the disk 743 Dirty: Memory which is waiting to get written back to the disk 744 Writeback: Memory which is actively being written back to the disk 745 AnonPages: Non-file backed pages mapped into userspace page tables 746 Mapped: files which have been mmaped, such as libraries 747 Slab: in-kernel data structures cache 748SReclaimable: Part of Slab, that might be reclaimed, such as caches 749 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure 750 PageTables: amount of memory dedicated to the lowest level of page 751 tables. 752NFS_Unstable: NFS pages sent to the server, but not yet committed to stable 753 storage 754 Bounce: Memory used for block device "bounce buffers" 755WritebackTmp: Memory used by FUSE for temporary writeback buffers 756 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), 757 this is the total amount of memory currently available to 758 be allocated on the system. This limit is only adhered to 759 if strict overcommit accounting is enabled (mode 2 in 760 'vm.overcommit_memory'). 761 The CommitLimit is calculated with the following formula: 762 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap 763 For example, on a system with 1G of physical RAM and 7G 764 of swap with a `vm.overcommit_ratio` of 30 it would 765 yield a CommitLimit of 7.3G. 766 For more details, see the memory overcommit documentation 767 in vm/overcommit-accounting. 768Committed_AS: The amount of memory presently allocated on the system. 769 The committed memory is a sum of all of the memory which 770 has been allocated by processes, even if it has not been 771 "used" by them as of yet. A process which malloc()'s 1G 772 of memory, but only touches 300M of it will only show up 773 as using 300M of memory even if it has the address space 774 allocated for the entire 1G. This 1G is memory which has 775 been "committed" to by the VM and can be used at any time 776 by the allocating application. With strict overcommit 777 enabled on the system (mode 2 in 'vm.overcommit_memory'), 778 allocations which would exceed the CommitLimit (detailed 779 above) will not be permitted. This is useful if one needs 780 to guarantee that processes will not fail due to lack of 781 memory once that memory has been successfully allocated. 782VmallocTotal: total size of vmalloc memory area 783 VmallocUsed: amount of vmalloc area which is used 784VmallocChunk: largest contiguous block of vmalloc area which is free 785 786.............................................................................. 787 788vmallocinfo: 789 790Provides information about vmalloced/vmaped areas. One line per area, 791containing the virtual address range of the area, size in bytes, 792caller information of the creator, and optional information depending 793on the kind of area : 794 795 pages=nr number of pages 796 phys=addr if a physical address was specified 797 ioremap I/O mapping (ioremap() and friends) 798 vmalloc vmalloc() area 799 vmap vmap()ed pages 800 user VM_USERMAP area 801 vpages buffer for pages pointers was vmalloced (huge area) 802 N<node>=nr (Only on NUMA kernels) 803 Number of pages allocated on memory node <node> 804 805> cat /proc/vmallocinfo 8060xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 807 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 8080xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 809 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 8100xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 811 phys=7fee8000 ioremap 8120xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 813 phys=7fee7000 ioremap 8140xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 8150xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 816 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 8170xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 818 pages=2 vmalloc N1=2 8190xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 820 /0x130 [x_tables] pages=4 vmalloc N0=4 8210xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 822 pages=14 vmalloc N2=14 8230xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 824 pages=4 vmalloc N1=4 8250xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 826 pages=2 vmalloc N1=2 8270xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 828 pages=10 vmalloc N0=10 829 830.............................................................................. 831 832softirqs: 833 834Provides counts of softirq handlers serviced since boot time, for each cpu. 835 836> cat /proc/softirqs 837 CPU0 CPU1 CPU2 CPU3 838 HI: 0 0 0 0 839 TIMER: 27166 27120 27097 27034 840 NET_TX: 0 0 0 17 841 NET_RX: 42 0 0 39 842 BLOCK: 0 0 107 1121 843 TASKLET: 0 0 0 290 844 SCHED: 27035 26983 26971 26746 845 HRTIMER: 0 0 0 0 846 RCU: 1678 1769 2178 2250 847 848 8491.3 IDE devices in /proc/ide 850---------------------------- 851 852The subdirectory /proc/ide contains information about all IDE devices of which 853the kernel is aware. There is one subdirectory for each IDE controller, the 854file drivers and a link for each IDE device, pointing to the device directory 855in the controller specific subtree. 856 857The file drivers contains general information about the drivers used for the 858IDE devices: 859 860 > cat /proc/ide/drivers 861 ide-cdrom version 4.53 862 ide-disk version 1.08 863 864More detailed information can be found in the controller specific 865subdirectories. These are named ide0, ide1 and so on. Each of these 866directories contains the files shown in table 1-6. 867 868 869Table 1-6: IDE controller info in /proc/ide/ide? 870.............................................................................. 871 File Content 872 channel IDE channel (0 or 1) 873 config Configuration (only for PCI/IDE bridge) 874 mate Mate name 875 model Type/Chipset of IDE controller 876.............................................................................. 877 878Each device connected to a controller has a separate subdirectory in the 879controllers directory. The files listed in table 1-7 are contained in these 880directories. 881 882 883Table 1-7: IDE device information 884.............................................................................. 885 File Content 886 cache The cache 887 capacity Capacity of the medium (in 512Byte blocks) 888 driver driver and version 889 geometry physical and logical geometry 890 identify device identify block 891 media media type 892 model device identifier 893 settings device setup 894 smart_thresholds IDE disk management thresholds 895 smart_values IDE disk management values 896.............................................................................. 897 898The most interesting file is settings. This file contains a nice overview of 899the drive parameters: 900 901 # cat /proc/ide/ide0/hda/settings 902 name value min max mode 903 ---- ----- --- --- ---- 904 bios_cyl 526 0 65535 rw 905 bios_head 255 0 255 rw 906 bios_sect 63 0 63 rw 907 breada_readahead 4 0 127 rw 908 bswap 0 0 1 r 909 file_readahead 72 0 2097151 rw 910 io_32bit 0 0 3 rw 911 keepsettings 0 0 1 rw 912 max_kb_per_request 122 1 127 rw 913 multcount 0 0 8 rw 914 nice1 1 0 1 rw 915 nowerr 0 0 1 rw 916 pio_mode write-only 0 255 w 917 slow 0 0 1 rw 918 unmaskirq 0 0 1 rw 919 using_dma 0 0 1 rw 920 921 9221.4 Networking info in /proc/net 923-------------------------------- 924 925The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 926additional values you get for IP version 6 if you configure the kernel to 927support this. Table 1-9 lists the files and their meaning. 928 929 930Table 1-8: IPv6 info in /proc/net 931.............................................................................. 932 File Content 933 udp6 UDP sockets (IPv6) 934 tcp6 TCP sockets (IPv6) 935 raw6 Raw device statistics (IPv6) 936 igmp6 IP multicast addresses, which this host joined (IPv6) 937 if_inet6 List of IPv6 interface addresses 938 ipv6_route Kernel routing table for IPv6 939 rt6_stats Global IPv6 routing tables statistics 940 sockstat6 Socket statistics (IPv6) 941 snmp6 Snmp data (IPv6) 942.............................................................................. 943 944 945Table 1-9: Network info in /proc/net 946.............................................................................. 947 File Content 948 arp Kernel ARP table 949 dev network devices with statistics 950 dev_mcast the Layer2 multicast groups a device is listening too 951 (interface index, label, number of references, number of bound 952 addresses). 953 dev_stat network device status 954 ip_fwchains Firewall chain linkage 955 ip_fwnames Firewall chain names 956 ip_masq Directory containing the masquerading tables 957 ip_masquerade Major masquerading table 958 netstat Network statistics 959 raw raw device statistics 960 route Kernel routing table 961 rpc Directory containing rpc info 962 rt_cache Routing cache 963 snmp SNMP data 964 sockstat Socket statistics 965 tcp TCP sockets 966 tr_rif Token ring RIF routing table 967 udp UDP sockets 968 unix UNIX domain sockets 969 wireless Wireless interface data (Wavelan etc) 970 igmp IP multicast addresses, which this host joined 971 psched Global packet scheduler parameters. 972 netlink List of PF_NETLINK sockets 973 ip_mr_vifs List of multicast virtual interfaces 974 ip_mr_cache List of multicast routing cache 975.............................................................................. 976 977You can use this information to see which network devices are available in 978your system and how much traffic was routed over those devices: 979 980 > cat /proc/net/dev 981 Inter-|Receive |[... 982 face |bytes packets errs drop fifo frame compressed multicast|[... 983 lo: 908188 5596 0 0 0 0 0 0 [... 984 ppp0:15475140 20721 410 0 0 410 0 0 [... 985 eth0: 614530 7085 0 0 0 0 0 1 [... 986 987 ...] Transmit 988 ...] bytes packets errs drop fifo colls carrier compressed 989 ...] 908188 5596 0 0 0 0 0 0 990 ...] 1375103 17405 0 0 0 0 0 0 991 ...] 1703981 5535 0 0 0 3 0 0 992 993In addition, each Channel Bond interface has its own directory. For 994example, the bond0 device will have a directory called /proc/net/bond0/. 995It will contain information that is specific to that bond, such as the 996current slaves of the bond, the link status of the slaves, and how 997many times the slaves link has failed. 998 9991.5 SCSI info 1000-------------
1001 1002If you have a SCSI host adapter in your system, you'll find a subdirectory 1003named after the driver for this adapter in /proc/scsi. You'll also see a list 1004of all recognized SCSI devices in /proc/scsi: 1005 1006 >cat /proc/scsi/scsi 1007 Attached devices: 1008 Host: scsi0 Channel: 00 Id: 00 Lun: 00 1009 Vendor: IBM Model: DGHS09U Rev: 03E0 1010 Type: Direct-Access ANSI SCSI revision: 03 1011 Host: scsi0 Channel: 00 Id: 06 Lun: 00 1012 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 1013 Type: CD-ROM ANSI SCSI revision: 02 1014 1015 1016The directory named after the driver has one file for each adapter found in 1017the system. These files contain information about the controller, including 1018the used IRQ and the IO address range. The amount of information shown is 1019dependent on the adapter you use. The example shows the output for an Adaptec 1020AHA-2940 SCSI adapter: 1021 1022 > cat /proc/scsi/aic7xxx/0 1023 1024 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 1025 Compile Options: 1026 TCQ Enabled By Default : Disabled 1027 AIC7XXX_PROC_STATS : Disabled 1028 AIC7XXX_RESET_DELAY : 5 1029 Adapter Configuration: 1030 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1031 Ultra Wide Controller 1032 PCI MMAPed I/O Base: 0xeb001000 1033 Adapter SEEPROM Config: SEEPROM found and used. 1034 Adaptec SCSI BIOS: Enabled 1035 IRQ: 10 1036 SCBs: Active 0, Max Active 2, 1037 Allocated 15, HW 16, Page 255 1038 Interrupts: 160328 1039 BIOS Control Word: 0x18b6 1040 Adapter Control Word: 0x005b 1041 Extended Translation: Enabled 1042 Disconnect Enable Flags: 0xffff 1043 Ultra Enable Flags: 0x0001 1044 Tag Queue Enable Flags: 0x0000 1045 Ordered Queue Tag Flags: 0x0000 1046 Default Tag Queue Depth: 8 1047 Tagged Queue By Device array for aic7xxx host instance 0: 1048 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1049 Actual queue depth per device for aic7xxx host instance 0: 1050 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1051 Statistics: 1052 (scsi0:0:0:0) 1053 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1054 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1055 Total transfers 160151 (74577 reads and 85574 writes) 1056 (scsi0:0:6:0) 1057 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1058 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1059 Total transfers 0 (0 reads and 0 writes) 1060 1061 10621.6 Parallel port info in /proc/parport 1063--------------------------------------- 1064 1065The directory /proc/parport contains information about the parallel ports of 1066your system. It has one subdirectory for each port, named after the port 1067number (0,1,2,...). 1068 1069These directories contain the four files shown in Table 1-10. 1070 1071 1072Table 1-10: Files in /proc/parport 1073.............................................................................. 1074 File Content 1075 autoprobe Any IEEE-1284 device ID information that has been acquired. 1076 devices list of the device drivers using that port. A + will appear by the 1077 name of the device currently using the port (it might not appear 1078 against any). 1079 hardware Parallel port's base address, IRQ line and DMA channel. 1080 irq IRQ that parport is using for that port. This is in a separate 1081 file to allow you to alter it by writing a new value in (IRQ 1082 number or none). 1083.............................................................................. 1084 10851.7 TTY info in /proc/tty 1086------------------------- 1087 1088Information about the available and actually used tty's can be found in the 1089directory /proc/tty.You'll find entries for drivers and line disciplines in 1090this directory, as shown in Table 1-11. 1091 1092 1093Table 1-11: Files in /proc/tty 1094.............................................................................. 1095 File Content 1096 drivers list of drivers and their usage 1097 ldiscs registered line disciplines 1098 driver/serial usage statistic and status of single tty lines 1099.............................................................................. 1100 1101To see which tty's are currently in use, you can simply look into the file 1102/proc/tty/drivers: 1103 1104 > cat /proc/tty/drivers 1105 pty_slave /dev/pts 136 0-255 pty:slave 1106 pty_master /dev/ptm 128 0-255 pty:master 1107 pty_slave /dev/ttyp 3 0-255 pty:slave 1108 pty_master /dev/pty 2 0-255 pty:master 1109 serial /dev/cua 5 64-67 serial:callout 1110 serial /dev/ttyS 4 64-67 serial 1111 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1112 /dev/ptmx /dev/ptmx 5 2 system 1113 /dev/console /dev/console 5 1 system:console 1114 /dev/tty /dev/tty 5 0 system:/dev/tty 1115 unknown /dev/tty 4 1-63 console 1116 1117 11181.8 Miscellaneous kernel statistics in /proc/stat 1119------------------------------------------------- 1120 1121Various pieces of information about kernel activity are available in the 1122/proc/stat file. All of the numbers reported in this file are aggregates 1123since the system first booted. For a quick look, simply cat the file: 1124 1125 > cat /proc/stat 1126 cpu 2255 34 2290 22625563 6290 127 456 0 0 1127 cpu0 1132 34 1441 11311718 3675 127 438 0 0 1128 cpu1 1123 0 849 11313845 2614 0 18 0 0 1129 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1130 ctxt 1990473 1131 btime 1062191376 1132 processes 2915 1133 procs_running 1 1134 procs_blocked 0 1135 softirq 183433 0 21755 12 39 1137 231 21459 2263 1136 1137The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1138lines. These numbers identify the amount of time the CPU has spent performing 1139different kinds of work. Time units are in USER_HZ (typically hundredths of a 1140second). The meanings of the columns are as follows, from left to right: 1141 1142- user: normal processes executing in user mode 1143- nice: niced processes executing in user mode 1144- system: processes executing in kernel mode 1145- idle: twiddling thumbs 1146- iowait: waiting for I/O to complete 1147- irq: servicing interrupts 1148- softirq: servicing softirqs 1149- steal: involuntary wait 1150- guest: running a normal guest 1151- guest_nice: running a niced guest 1152 1153The "intr" line gives counts of interrupts serviced since boot time, for each 1154of the possible system interrupts. The first column is the total of all 1155interrupts serviced; each subsequent column is the total for that particular 1156interrupt. 1157 1158The "ctxt" line gives the total number of context switches across all CPUs. 1159 1160The "btime" line gives the time at which the system booted, in seconds since 1161the Unix epoch. 1162 1163The "processes" line gives the number of processes and threads created, which 1164includes (but is not limited to) those created by calls to the fork() and 1165clone() system calls. 1166 1167The "procs_running" line gives the total number of threads that are 1168running or ready to run (i.e., the total number of runnable threads). 1169 1170The "procs_blocked" line gives the number of processes currently blocked, 1171waiting for I/O to complete. 1172 1173The "softirq" line gives counts of softirqs serviced since boot time, for each 1174of the possible system softirqs. The first column is the total of all 1175softirqs serviced; each subsequent column is the total for that particular 1176softirq. 1177 1178 11791.9 Ext4 file system parameters 1180------------------------------ 1181 1182Information about mounted ext4 file systems can be found in 1183/proc/fs/ext4. Each mounted filesystem will have a directory in 1184/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1185/proc/fs/ext4/dm-0). The files in each per-device directory are shown 1186in Table 1-12, below. 1187 1188Table 1-12: Files in /proc/fs/ext4/<devname> 1189.............................................................................. 1190 File Content 1191 mb_groups details of multiblock allocator buddy cache of free blocks 1192.............................................................................. 1193 11942.0 /proc/consoles 1195------------------ 1196Shows registered system console lines. 1197 1198To see which character device lines are currently used for the system console 1199/dev/console, you may simply look into the file /proc/consoles: 1200 1201 > cat /proc/consoles 1202 tty0 -WU (ECp) 4:7 1203 ttyS0 -W- (Ep) 4:64 1204 1205The columns are: 1206 1207 device name of the device 1208 operations R = can do read operations 1209 W = can do write operations 1210 U = can do unblank 1211 flags E = it is enabled 1212 C = it is preferred console 1213 B = it is primary boot console 1214 p = it is used for printk buffer 1215 b = it is not a TTY but a Braille device 1216 a = it is safe to use when cpu is offline 1217 major:minor major and minor number of the device separated by a colon 1218 1219------------------------------------------------------------------------------ 1220Summary 1221------------------------------------------------------------------------------ 1222The /proc file system serves information about the running system. It not only 1223allows access to process data but also allows you to request the kernel status 1224by reading files in the hierarchy. 1225 1226The directory structure of /proc reflects the types of information and makes 1227it easy, if not obvious, where to look for specific data. 1228------------------------------------------------------------------------------ 1229 1230------------------------------------------------------------------------------ 1231CHAPTER 2: MODIFYING SYSTEM PARAMETERS 1232------------------------------------------------------------------------------ 1233 1234------------------------------------------------------------------------------ 1235In This Chapter 1236------------------------------------------------------------------------------ 1237* Modifying kernel parameters by writing into files found in /proc/sys 1238* Exploring the files which modify certain parameters 1239* Review of the /proc/sys file tree 1240------------------------------------------------------------------------------ 1241 1242 1243A very interesting part of /proc is the directory /proc/sys. This is not only 1244a source of information, it also allows you to change parameters within the 1245kernel. Be very careful when attempting this. You can optimize your system, 1246but you can also cause it to crash. Never alter kernel parameters on a 1247production system. Set up a development machine and test to make sure that 1248everything works the way you want it to. You may have no alternative but to 1249reboot the machine once an error has been made. 1250 1251To change a value, simply echo the new value into the file. An example is 1252given below in the section on the file system data. You need to be root to do 1253this. You can create your own boot script to perform this every time your 1254system boots. 1255 1256The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1257general things in the operation of the Linux kernel. Since some of the files 1258can inadvertently disrupt your system, it is advisable to read both 1259documentation and source before actually making adjustments. In any case, be 1260very careful when writing to any of these files. The entries in /proc may 1261change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1262review the kernel documentation in the directory /usr/src/linux/Documentation. 1263This chapter is heavily based on the documentation included in the pre 2.2 1264kernels, and became part of it in version 2.2.1 of the Linux kernel. 1265 1266Please see: Documentation/sysctl/ directory for descriptions of these 1267entries. 1268 1269------------------------------------------------------------------------------ 1270Summary 1271------------------------------------------------------------------------------ 1272Certain aspects of kernel behavior can be modified at runtime, without the 1273need to recompile the kernel, or even to reboot the system. The files in the 1274/proc/sys tree can not only be read, but also modified. You can use the echo 1275command to write value into these files, thereby changing the default settings 1276of the kernel. 1277------------------------------------------------------------------------------ 1278 1279------------------------------------------------------------------------------ 1280CHAPTER 3: PER-PROCESS PARAMETERS 1281------------------------------------------------------------------------------ 1282 12833.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score 1284-------------------------------------------------------------------------------- 1285 1286These file can be used to adjust the badness heuristic used to select which 1287process gets killed in out of memory conditions. 1288 1289The badness heuristic assigns a value to each candidate task ranging from 0 1290(never kill) to 1000 (always kill) to determine which process is targeted. The 1291units are roughly a proportion along that range of allowed memory the process 1292may allocate from based on an estimation of its current memory and swap use. 1293For example, if a task is using all allowed memory, its badness score will be 12941000. If it is using half of its allowed memory, its score will be 500. 1295 1296There is an additional factor included in the badness score: root 1297processes are given 3% extra memory over other tasks. 1298 1299The amount of "allowed" memory depends on the context in which the oom killer 1300was called. If it is due to the memory assigned to the allocating task's cpuset 1301being exhausted, the allowed memory represents the set of mems assigned to that 1302cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed 1303memory represents the set of mempolicy nodes. If it is due to a memory 1304limit (or swap limit) being reached, the allowed memory is that configured 1305limit. Finally, if it is due to the entire system being out of memory, the 1306allowed memory represents all allocatable resources. 1307 1308The value of /proc/<pid>/oom_score_adj is added to the badness score before it 1309is used to determine which task to kill. Acceptable values range from -1000 1310(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to 1311polarize the preference for oom killing either by always preferring a certain 1312task or completely disabling it. The lowest possible value, -1000, is 1313equivalent to disabling oom killing entirely for that task since it will always 1314report a badness score of 0. 1315 1316Consequently, it is very simple for userspace to define the amount of memory to 1317consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for 1318example, is roughly equivalent to allowing the remainder of tasks sharing the 1319same system, cpuset, mempolicy, or memory controller resources to use at least 132050% more memory. A value of -500, on the other hand, would be roughly 1321equivalent to discounting 50% of the task's allowed memory from being considered 1322as scoring against the task. 1323 1324For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also 1325be used to tune the badness score. Its acceptable values range from -16 1326(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17 1327(OOM_DISABLE) to disable oom killing entirely for that task. Its value is 1328scaled linearly with /proc/<pid>/oom_score_adj. 1329 1330Writing to /proc/<pid>/oom_score_adj or /proc/<pid>/oom_adj will change the 1331other with its scaled value. 1332 1333The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last 1334value set by a CAP_SYS_RESOURCE process. To reduce the value any lower 1335requires CAP_SYS_RESOURCE. 1336 1337NOTICE: /proc/<pid>/oom_adj is deprecated and will be removed, please see 1338Documentation/feature-removal-schedule.txt. 1339 1340Caveat: when a parent task is selected, the oom killer will sacrifice any first 1341generation children with separate address spaces instead, if possible. This 1342avoids servers and important system daemons from being killed and loses the 1343minimal amount of work. 1344 1345 13463.2 /proc/<pid>/oom_score - Display current oom-killer score 1347------------------------------------------------------------- 1348 1349This file can be used to check the current score used by the oom-killer is for 1350any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which 1351process should be killed in an out-of-memory situation. 1352 1353 13543.3 /proc/<pid>/io - Display the IO accounting fields 1355------------------------------------------------------- 1356 1357This file contains IO statistics for each running process 1358 1359Example 1360------- 1361 1362test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1363[1] 3828 1364 1365test:/tmp # cat /proc/3828/io 1366rchar: 323934931 1367wchar: 323929600 1368syscr: 632687 1369syscw: 632675 1370read_bytes: 0 1371write_bytes: 323932160 1372cancelled_write_bytes: 0 1373 1374 1375Description 1376----------- 1377 1378rchar 1379----- 1380 1381I/O counter: chars read 1382The number of bytes which this task has caused to be read from storage. This 1383is simply the sum of bytes which this process passed to read() and pread(). 1384It includes things like tty IO and it is unaffected by whether or not actual 1385physical disk IO was required (the read might have been satisfied from 1386pagecache) 1387 1388 1389wchar 1390----- 1391 1392I/O counter: chars written 1393The number of bytes which this task has caused, or shall cause to be written 1394to disk. Similar caveats apply here as with rchar. 1395 1396 1397syscr 1398----- 1399 1400I/O counter: read syscalls 1401Attempt to count the number of read I/O operations, i.e. syscalls like read() 1402and pread(). 1403 1404 1405syscw 1406----- 1407 1408I/O counter: write syscalls 1409Attempt to count the number of write I/O operations, i.e. syscalls like 1410write() and pwrite(). 1411 1412 1413read_bytes 1414---------- 1415 1416I/O counter: bytes read 1417Attempt to count the number of bytes which this process really did cause to 1418be fetched from the storage layer. Done at the submit_bio() level, so it is 1419accurate for block-backed filesystems. <please add status regarding NFS and 1420CIFS at a later time> 1421 1422 1423write_bytes 1424----------- 1425 1426I/O counter: bytes written 1427Attempt to count the number of bytes which this process caused to be sent to 1428the storage layer. This is done at page-dirtying time. 1429 1430 1431cancelled_write_bytes 1432--------------------- 1433 1434The big inaccuracy here is truncate. If a process writes 1MB to a file and 1435then deletes the file, it will in fact perform no writeout. But it will have 1436been accounted as having caused 1MB of write. 1437In other words: The number of bytes which this process caused to not happen, 1438by truncating pagecache. A task can cause "negative" IO too. If this task 1439truncates some dirty pagecache, some IO which another task has been accounted 1440for (in its write_bytes) will not be happening. We _could_ just subtract that 1441from the truncating task's write_bytes, but there is information loss in doing 1442that. 1443 1444 1445Note 1446---- 1447 1448At its current implementation state, this is a bit racy on 32-bit machines: if 1449process A reads process B's /proc/pid/io while process B is updating one of 1450those 64-bit counters, process A could see an intermediate result. 1451 1452 1453More information about this can be found within the taskstats documentation in 1454Documentation/accounting. 1455 14563.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1457--------------------------------------------------------------- 1458When a process is dumped, all anonymous memory is written to a core file as 1459long as the size of the core file isn't limited. But sometimes we don't want 1460to dump some memory segments, for example, huge shared memory. Conversely, 1461sometimes we want to save file-backed memory segments into a core file, not 1462only the individual files. 1463 1464/proc/<pid>/coredump_filter allows you to customize which memory segments 1465will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1466of memory types. If a bit of the bitmask is set, memory segments of the 1467corresponding memory type are dumped, otherwise they are not dumped. 1468 1469The following 7 memory types are supported: 1470 - (bit 0) anonymous private memory 1471 - (bit 1) anonymous shared memory 1472 - (bit 2) file-backed private memory 1473 - (bit 3) file-backed shared memory 1474 - (bit 4) ELF header pages in file-backed private memory areas (it is 1475 effective only if the bit 2 is cleared) 1476 - (bit 5) hugetlb private memory 1477 - (bit 6) hugetlb shared memory 1478 1479 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1480 are always dumped regardless of the bitmask status. 1481 1482 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only 1483 effected by bit 5-6. 1484 1485Default value of coredump_filter is 0x23; this means all anonymous memory 1486segments and hugetlb private memory are dumped. 1487 1488If you don't want to dump all shared memory segments attached to pid 1234, 1489write 0x21 to the process's proc file. 1490 1491 $ echo 0x21 > /proc/1234/coredump_filter 1492 1493When a new process is created, the process inherits the bitmask status from its 1494parent. It is useful to set up coredump_filter before the program runs. 1495For example: 1496 1497 $ echo 0x7 > /proc/self/coredump_filter 1498 $ ./some_program 1499 15003.5 /proc/<pid>/mountinfo - Information about mounts 1501-------------------------------------------------------- 1502 1503This file contains lines of the form: 1504 150536 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1506(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1507 1508(1) mount ID: unique identifier of the mount (may be reused after umount) 1509(2) parent ID: ID of parent (or of self for the top of the mount tree) 1510(3) major:minor: value of st_dev for files on filesystem 1511(4) root: root of the mount within the filesystem 1512(5) mount point: mount point relative to the process's root 1513(6) mount options: per mount options 1514(7) optional fields: zero or more fields of the form "tag[:value]" 1515(8) separator: marks the end of the optional fields 1516(9) filesystem type: name of filesystem of the form "type[.subtype]" 1517(10) mount source: filesystem specific information or "none" 1518(11) super options: per super block options 1519 1520Parsers should ignore all unrecognised optional fields. Currently the 1521possible optional fields are: 1522 1523shared:X mount is shared in peer group X 1524master:X mount is slave to peer group X 1525propagate_from:X mount is slave and receives propagation from peer group X (*) 1526unbindable mount is unbindable 1527 1528(*) X is the closest dominant peer group under the process's root. If 1529X is the immediate master of the mount, or if there's no dominant peer 1530group under the same root, then only the "master:X" field is present 1531and not the "propagate_from:X" field. 1532 1533For more information on mount propagation see: 1534 1535 Documentation/filesystems/sharedsubtree.txt 1536 1537 15383.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1539-------------------------------------------------------- 1540These files provide a method to access a tasks comm value. It also allows for 1541a task to set its own or one of its thread siblings comm value. The comm value 1542is limited in size compared to the cmdline value, so writing anything longer 1543then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1544comm value. 1545